107 lines
5.2 KiB
JavaScript
107 lines
5.2 KiB
JavaScript
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module.exports = function(RED) {
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"use strict";
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var ExifImage = require('exif').ExifImage;
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function convertDegreesMinutesSecondsToDecimals(degrees, minutes, seconds) {
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var result;
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result = degrees + (minutes / 60) + (seconds / 3600);
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return result;
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}
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function ExifNode(n) {
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RED.nodes.createNode(this,n);
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var node = this;
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/***
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* Extracts GPS location information from Exif data. If enough information is
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* provided, convert the Exif data into a pair of single floating point number
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* latitude/longitude data pairs. Populates msg.location with these.
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* Assumes that the msg object will always have exifData available as msg.exif.
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* Assume that the GPS data saved into Exif provides a valid value
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*/
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function addMsgLocationDataFromExifGPSData(msg) {
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var gpsData = msg.exif.gps; // declaring variable purely to make checks more readable
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if (gpsData.GPSAltitude) {
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/* istanbul ignore else */
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if (!msg.location) { msg.location = {}; }
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msg.location.alt = gpsData.GPSAltitude;
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}
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if (gpsData.GPSLatitudeRef && gpsData.GPSLatitude && gpsData.GPSLongitudeRef && gpsData.GPSLongitude) { // location can be determined, OK
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// The data provided in Exif is in degrees, minutes, seconds, this is to be converted into a single floating point degree
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if (gpsData.GPSLatitude.length === 3) { // OK to convert latitude
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if (gpsData.GPSLongitude.length === 3) { // OK to convert longitude
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var latitude = convertDegreesMinutesSecondsToDecimals(gpsData.GPSLatitude[0], gpsData.GPSLatitude[1], gpsData.GPSLatitude[2]);
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latitude = Math.round(latitude * 100000)/100000; // 5dp is approx 1m resolution...
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// (N)orth means positive latitude, (S)outh means negative latitude
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if (gpsData.GPSLatitudeRef.toString() === 'S' || gpsData.GPSLatitudeRef.toString() === 's') {
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latitude = latitude * -1;
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}
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var longitude = convertDegreesMinutesSecondsToDecimals(gpsData.GPSLongitude[0], gpsData.GPSLongitude[1], gpsData.GPSLongitude[2]);
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longitude = Math.round(longitude * 100000)/100000; // 5dp is approx 1m resolution...
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// (E)ast means positive longitude, (W)est means negative longitude
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if (gpsData.GPSLongitudeRef.toString() === 'W' || gpsData.GPSLongitudeRef.toString() === 'w') {
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longitude = longitude * -1;
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}
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// Create location property if not exists
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if (!msg.location) { msg.location = {}; }
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msg.location.lat = latitude;
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msg.location.lon = longitude;
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return;
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}
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else {
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node.log("Invalid longitude data, no location information has been added to the message.");
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}
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}
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else {
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node.log("Invalid latitude data, no location information has been added to the message.");
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}
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}
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else {
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node.log("The location of this image cannot be determined safely so no location information has been added to the message.");
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}
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}
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this.on("input", function(msg) {
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try {
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if (msg.payload) {
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if (Buffer.isBuffer(msg.payload)) {
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new ExifImage({ image : msg.payload }, function (error, exifData) {
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if (error) {
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node.log(error.toString());
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}
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else {
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//msg.payload remains the same buffer
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if ((exifData) && (exifData.hasOwnProperty("gps")) && (Object.keys(exifData.gps).length !== 0)) {
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msg.exif = exifData;
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addMsgLocationDataFromExifGPSData(msg);
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}
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else {
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node.warn("The incoming image did not contain Exif GPS data, nothing to do. ");
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}
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}
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node.send(msg);
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});
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}
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else {
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node.error("Invalid payload received, the Exif node cannot proceed, no messages sent.");
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return;
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}
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}
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else {
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node.error("No payload received, the Exif node cannot proceed, no messages sent.");
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return;
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}
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}
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catch (error) {
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node.error("An error occurred while extracting Exif information. Please check the log for details.");
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node.log('Error: '+error.message);
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return;
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}
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});
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}
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RED.nodes.registerType("exif",ExifNode);
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}
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